I think it was error U163.
Well I haven't been able to find anything on this anywhere so I played around with the buttons to find a hidden workaround.
There is one! I pushed simultaneously "OK" and "Black (start button)" and "Stop" and the error page went away and it started printing.
These printers are maddening if you don't know the workarounds since it won't otherwise even let me fax or scan until I gave its ridiculously expensive cartridge.
Any other workaround that people know of?
